Turkish Prime Minister Recep Tayyip Erdogan said Sunday it was his “duty’’ to order riot police to evict activists occupying an Istanbul park that became a center of defiance against his rule, even as the government crackdown continued across town with tear gas fired at protesters trying to regroup.

In a thunderous speech to supporters in western Istanbul, Erdogan recalled telling Interior Ministry officials: “‘You are going to clear Gezi Park. We have reached an end. We cannot stand it anymore.’ And as you know, yesterday the operation was carried out, and it was cleared. I did my duty as prime minister. Otherwise there would be no point in my being in office.’’

About 10 km away in central Istanbul, riot police fired tear gas and used water cannons on thousands of defiant protesters attempting to regroup and demonstrate again in the city’s main Taksim Square. Clashes broke out in nearby neighborhoods with stone-throwing youths.

Police in uniform and plain clothes sealed off Taksim Square and Gezi Park, which riot police cleared of thousands of peaceful protesters in a swift but muscular operation Saturday evening. Crews worked through the night to remove all traces of a sit-in that started more than two weeks ago and became the focus of the strongest challenge to Erdogan in his 10 years in office.

Istanbul’s governor, Huseyin Avni Mutlu, said the square was off-limits to the public for the time being, and nobody would be allowed to gather. A spokesman for the protesters vowed the group would retake Gezi Park.

As dusk fell Saturday, hundreds of white-helmeted riot police swept through the park and adjacent Taksim Square, firing canisters of the acrid, stinging gas. Thousands of peaceful protesters, choking on the fumes and stumbling among the tents, put up little physical resistance.